EP0030595B1 - Appareil de correction pour un tube à rayons cathodiques - Google Patents

Appareil de correction pour un tube à rayons cathodiques Download PDF

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Publication number
EP0030595B1
EP0030595B1 EP80106262A EP80106262A EP0030595B1 EP 0030595 B1 EP0030595 B1 EP 0030595B1 EP 80106262 A EP80106262 A EP 80106262A EP 80106262 A EP80106262 A EP 80106262A EP 0030595 B1 EP0030595 B1 EP 0030595B1
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EP
European Patent Office
Prior art keywords
digital
circuit
screen
cathode
ray tube
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Expired
Application number
EP80106262A
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German (de)
English (en)
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EP0030595A1 (fr
Inventor
Stanislaw Wrona
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International Business Machines Corp
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International Business Machines Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/16—Picture reproducers using cathode ray tubes
    • H04N9/28—Arrangements for convergence or focusing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00—Diagnosis, testing or measuring for television systems or their details
    • H04N17/04—Diagnosis, testing or measuring for television systems or their details for receivers

Definitions

  • This invention relates to cathode-ray tube display apparatus with beam convergence correction circuits for the correction of misconvergence in a shadow mask cathode-ray tube.
  • a shadow mask is a parallax device for ensuring colour purity in colour cathode-ray tubes, i.e that beams from respective electron guns land only on respective different phosphors which emit different colours when activated by an electron beam.
  • the pattern in which each phosphor is deposited on the screen face is identical to a pattern of apertures in the shadow mask but each pattern is slightly displaced from the others to allow each electron gun to see through the apertures only the phosphor it is intended to activate.
  • the patterns usually found are sets of round holes or perpendicular rows of slits, such as in precision in-line tubes, or perpendicular slits extending from top to bottom of the screen, such as in aperture grid tubes.
  • a problem associated with shadow mask tubes is that of ensuring that beams from different guns coincide at the shadow mask. This ensures that corresponding elements of the phosphor patterns are activated simultaneously by the electron guns so that mixtures of primary colours can produce clearly defined secondary colours. If such coincidence does not occur, separate colours are visible.
  • the problem is called the convergence problem and is to some -extent subjective, in that a certain degree of misconvergence is not visible to, or can be tolerated by, the viewer of a domestic television set, whereas the same degree of misconvergence would not be acceptable to a viewer, at perhaps one metre from the screen, using a colour tube as a data display terminal.
  • a disadvantage of the digital convergence correction technique outlined above is its cost.
  • four correction factors are required, namely a correction factor for each beam, and a correction factor for the blue lateral coil. If the screen is divided into 256 areas, 1 K byte of storage is required. This is a not insignificant overhead in the cost of a colour display terminal.
  • British Patent Specification 1,586,045 describes a convergence correction circuit using a pair of programmable read only memories (PROMs) which receive beam horizontal and vertical address information. Digital outputs of each PROM are supplied to digital to analogue converters to generate voltages corresponding to four quadrants of the screen and which are applied to the convergence correction coils after summing independently adjustable proportions of the generated voltages. The voltages at the outputs of the digital to analogue converters are stepped parabolas which can be varied in accordance with the contents of the PROMs.
  • PROMs programmable read only memories
  • cathode-ray tube display apparatus comprises a shadow-mask colour cathode-ray tube, means adapted to scan the screen of the cathode-ray tube with electron beams to display information, analogue circuit means adapted to generate convergence correction waveforms for the electron beams as they scan the screen, a writable digital store for storing digital values used in the generation of said convergence correction waveforms, means for presenting stored digital values to said circuit means in accordance with the position of the beams as they scan the screen, and means for changing the stored digital values to correct a test pattern displayed on said screen, characterised in that said circuit means includes polynomial generation circuits each arranged in operation to generate a waveform of polynomial form from each cycle of a sawtooth input signal wherein the output of each polynomial generation circuit is connected to a plurality of signal channels, each channel including a respective scaling circuit which determines the size of the polynomial waveform transmitted on the channel in accordance with at least some of said stored digital parameters.
  • beam control information is supplied over a channel 1 to a colour cathode-ray tube (not shown).
  • the control information which is deflection control information, is generated by analogue circuitry 2 which has as inputs analogue signals representing the desired positions of the tube beams and analogue signals derived from stored digital parameters.
  • the beam position signals are supplied to analogue circuitry 2 over conductors 3 and 4, respectively.
  • the signals on conductor 3 represent the desired X coordinate of the tube beams, and the signals on conductor 4 represent the desired Y coordinate of the tube beams.
  • a digital store 5 contains parameters of the calculations effected by circuitry 2.
  • FIG. 1 illustrates an important advantage of the invention, in that the contents of digital store 5 may readily be changed by means of a keyboard 7, or other suitable interactive device.
  • the correction of misconvergence in a colour cathode-ray tube involves static and dynamic convergence.
  • Static convergence involves influencing the electron beams by permanent magnetic fields which are adjusted to bring the beams into coincidence at the centre of the screen. Convergence over the rest of the screen is effected by continuously varying magnetic fields whose strengths depend on the positions of the beams on the screen.
  • In a delta gun tube there are four dynamic convergence fields, three of which modify respectively the deflection of three beams, and the fourth of which modifies the lateral position of the blue beam, or in some arrangements of all three beams.
  • In-line tubes use four dynamic convergence fields, affecting horizontal and vertical movement of the outer two beams.
  • Figure 2 is a block diagram of apparatus which uses inter alia, parabolic correction currents in adjusting the convergence of a delta gun cathode-ray tube in which the beams are constrained to trace a horizontal raster.
  • conductors 3 and 4 receive, respectively, the line and frame timebases, which are, as indicated in Figure 2, sawtooth waveforms.
  • the line timebase on conductor 3 is converted by a circuit 8H into parabolas, one parabola for each repetition of the line timebase.
  • Outputs from circuit 8H are connected to summing circuits 9R, 9G, 9B, and 9L and to a corner correction circuit 10.
  • each circuit 11 includes a digital-to-analogue converter which receives at an input 12 a digital value. The digital value determines the size of the parabola received at the summing circuit. Effectively each scaling circuit multiplies a parabolic waveform by a constant. The constant is selectable and, preferably, is supplied from a digital store. A similar arrangement is provided for the frame timebase on conductor 4. A circuit 8V generates a parabola during each repetition of the frame timebase. Scaling circuits 11 determine the size of the parabola supplied to the summing circuits.
  • Outputs from circuit 8V are connected through scaling circuits 11 to summing circuits 9R, 9G, and 9B but not to circuit 9L.
  • Circuit 8V also has an output connected to corner correction circuit 10. The latter generates the product of the line and frame timebases, i.e. it generates a function X.Y.
  • the output of circuit 10 is connected through scaling circuits 11 to the summing circuits 9R, 9G, 9B and 9L.
  • Each summing circuit is connected to respective deflection correction coils 12R, 12G, 12B and 12L, which are arranged in known manner to modify the deflection given to the electron beams by the main deflection coils so as to correct misconvergence of the beams.
  • the circuitry of Figure 2 has the advantage over known analogue convergence correction circuitry that the correction currents in the coils 12R, 12G, 12B and 12L can readily be varied by varying the digital inputs to the scaling circuits 11.
  • the digital values are held in a store and it is a relatively simple matter to change the values, for example, by use of a keyboard as described in our British Patent 1,517,119. Further, different digital values can be read from the store as the screen is traversed by the electron beams, thus enabling more accurate correction with relatively simple analogue circuitry.
  • One suitable procedure is to envisage the screen as divided into four quadrants by the horizontal and vertical axes passing through the centre of the screen.
  • FIG. 3 shows the circuit on which the circuits 8H, 8V of Figure 2 are based.
  • An operational amplifier 13 has diodes D1, D2, series-connected between the output and the negative input to the amplifier.
  • a current source I in is also connected to the negative input.
  • the positive input of the amplifier 12 is connected to ground through a diode D4 and to a reference current I ref .
  • Output current lout is taken from the output of the amplifier 13 through a diode D3.
  • the diode equation is used: where I d is the diode current and V d the voltage across the diode. I ds and V o are constants of the diode.
  • V dl is the voltage across diode D1, and similarly for the other diodes. If it is assumed that the diodes are matched, so that I ds and V are the same for each diode: This gives: Since I ds is much smaller than the other currents it can be disregarded, giving:
  • the output current is a quadratic function of the input current multiplied by a constant, determined by the reference current.
  • cubic functions of the input current can be obtained by connecting three diodes in series between the output and input of the amplifier 12 and by adding another diode in series with D4.
  • other functions can be obtained, for example, using three diodes in the feedback loop and two at the output gives a output current proportional to the power 3/2 of the input current, or using single diodes in the feedback loop and at the output with two diodes instead of the single diode D4 gives an output current proportional to the reciprocal of the input current.
  • the polarities of all the diodes and the current sources may be reversed without affecting operation of the circuit although in this case the polarity of the output is also reversed.
  • the output of the circuit can be varied by varying I ref .
  • I ref and the diode D4 thus correspond to a scaling circuit 11, shown in Figure 2.
  • a diode and resistor are used to tie the quiescent output level to ground.
  • the diode D is connected in series with D4 and the resistor R", equal in value to R, is connected between the diode D and the negative input terminal of amplifier 14.
  • Figure 5 is a circuit diagram of circuit 8H, the scaling circuits 11 connected to circuit 8H and the connection between circuit 8H and corner correction circuit 10, all shown in Figure 2.
  • the negative terminal of operational amplifier 1 is connected to conductor 3 through resistor R1.
  • the output terminal 16 is connected through two feedback paths to the negative input terminal.
  • the first path comprises series-connected diodes D5 and D6, while the second path contains series-connected diodes D7, D8, connected in the opposite direction to the diodes D5, D6.
  • Output terminal 16 of amplifier 14 is also connected through respective diodes D9 to D12 to four scaling circuits 11.
  • the positive terminal 17 of amplifier 1 is connected to ground and to the positive terminal 19 of an operational amplifier 18.
  • the negative terminal 20 of amplifier 18 is connected to output terminal 16 of amplifier 14 through a resistor R2.
  • a resistor R3 connects the output 21 of amplifier 18 to the negative terminal 20.
  • Output 21 is also connected through respective diodes D13 to D16 to each scaling circuit 11.
  • the scaling circuits 11 are connected, respectively, to terminals HR, HG, HB and HL.
  • the output terminal 16 of amplifier 14 is connected through diodes D17 and D18 to the negative terminal 23 of an operational amplifier 22.
  • the output terminal 21 of amplifier 18 is connected to the terminal 23 through diodes D19 and D18.
  • the output terminal 24 of amplifier 22 is connected to a terminal HC and through diodes D20 and D21 to the negative terminal 23.
  • the positive terminal 25 of amplifier 22 is connected to ground.
  • Each scaling circuit 11 is of identical construction and is as shown in Figure 5 consisting of an operational amplifier 26 and a digital-to-analogue converter 27 of the kind which incorporates a digital register so that it is not necessary that the digital input is maintained to maintain the analogue output.
  • the analogue output terminal 28 of the converter 27 is connected through diode D20 to the positive terminal 29 of amplifier 26. Dode D20 and terminal 29 are connected to ground through diode D21.
  • Terminal 28 of converter 27 is connected to the negative terminal 30 of amplifier 26 through resistor R4.
  • the output terminal 31 of amplifier 26 is connected to negative terminal 30 through resistor R5.
  • the digital input to converter 27 is received on terminal 32, which in practice consists of a set of terminals providing a parallel input to the converter 27.
  • the correction waveform produced by the circuitry of Figure 5 is parabolic in shape and is derived from a sawtooth waveform on conductor 3 which has peaks and troughs symmetrical with respect to ground. This necessitates the two parallel feedback loops between output ter- rriinal 16 and the negative input terminal of amplifier 15 since one pair of diodes D5, D6 or D7, D8 is non-conductive during the positive and negative halves, respectively, of the input waveform.
  • the output of amplifier 14 consists of positive and negative half-waveforms of which the negative portions are blocked by diodes D9 to D12 and D17.
  • Amplifier 18 inverts the negative half-waveform so that it is passed by diodes D13 to D16 and D19.
  • Each scaling circuit 11 consists of a digital-to-analogue converter 27, which may be for example a Motorola MC 1408-8L, which is connected to a digital store by way of terminal 32.
  • Terminal 32 is representative of eight such terminals at which eight bits are available in parallel from the digital store.
  • the converter 27 incorporates storage devices in which the input bits are retained.
  • At terminal HC is provided a waveform used in generating the correction to be applied at the corners of the screen.
  • Amplifier 22 and diodes D18, D20 and D21 transform the parabolic waveform present at the cathodes of diodes D17 and D19 into a linear waveform representative of the X coordinate.
  • Figure 6 shows the circuit 8V of Figure 2 and its connection to the corner correction circuit 10. Comparison of Figures 5 and 6 shows that the circuits are identical except for the absence of one output channel.
  • the lateral correction coil does not require a vertical coordinate input.
  • the input to the circuit of Figure 6 is the sawtooth frame timebase which determines the Y coordinate of the beams. This is converted to a parabola which is scaled by the scaling circuits 11, parabolic outputs of sizes determined by the scaling circuits being provided at the terminals VR, VG and VB. As explained with reference to Figure 5, a linear output representative, in this case, of Y appears at terminal VC.
  • Figure 7 shows the corner correction circuit 10 of Figure 2.
  • the circuit is designed to produce the signal X.Y.
  • the terminal VC and HC are connected respectively through resistors R6 and R7 to the negative input terminal of an operational amplifier 33.
  • the output terminal of amplifier 33 is connected through parallel- connected diodes D22 to D25 to respective scaling circuits.
  • the outputs of the scaling circuits are connected respectively to terminals CR, CG, CB and CL.
  • the positive input of amplifier 33 is grounded while the output is connected to the negative input through a resistor R8.
  • the effect of the circuit of Figure 7 is to multiply the linear signals representing X and Y coordinates of the beam position to give the function X.Y.
  • the function is then scaled by the circuits 11 to produce the required magnitude outputs at terminals CR, CG, CB and CL.
  • FIG 8 shows how the signals and the output terminals shown in Figures 4, 5 and 6 are combined to provide correction currents to the correction coils 12R, 12G, 12B and 12L of Figure 2.
  • each correction coil has a similar control circuit and the following description is only of the circuit associated with the coil 12R, which is the coil designed to influence the electron beam from the red gun.
  • the terminals HR, VR and CR are connected through equal resistors R to the negative terminal of an operational amplifier 35, of which the positive terminal is connected to ground and the output to the base of a transistor T1.
  • the collector of transistor T1 is connected to voltage source of potential +V, and the emitter to one end of correction coil 12R.
  • a digital-to-analogue converter 36 of the same kind as converter 27 of Figure 5, is connected to the other end of correction coil 12R, which is also connected to ground through a resistor R10.
  • the resistance network consisting of resistors R sums the inputs at terminals Hr, Vr and Cr to obtain a voltage which is applied to the base of transistor T1 to control the current flowing through the transistor, the correction coil 12R, and resistor R10 to ground.
  • the absolute value of the current is determined by digital-to-analogue converter 36. The higher the current generated by converter 36, the less current is drawn through coil 12R. It is envisaged that the setting of converter 36 will not be changed except to correct long-term drift, so it could be replaced by a potentiometer. It is more convenient, however, to store digital values to be supplied to the converters 36 and to adjust these values, for example, by means of a keyboard, than to use potentiometers.
  • the procedure for storing and transmitting the digital values to the digital-to-analogue converters is preferably that described in British Patent Specification 1,517,119, referred to above.
  • Digital values are held in a store.
  • Counters operate, in known manner, to generate numbers representing the position of the electron beams on the screen.
  • the counters may be synchronised with the line and frame timebases, for example, the counter holding the count representing the number of the line is stepped by horizontal flyback and reset by vertical flyback.
  • the counter may be the basic timers from which the line and frame timebases are derived. Such arrangements are well-known in the art and will not be described here.
  • As particular counts are reached signals are transmitted to the store to read appropriate sets of digital values to the analogue-to-digital converters.
  • the digital values change at most in each quadrant of the screen.
  • the four horizontal, three vertical and four corner values for each quadrant can readily be stored in four storage locations, one assigned to each quadrant.
  • the contents of the storage locations are read to a register connected to the analogue-to-digital converters.
  • An alternative arrangement which avoids the need to allow for the digital-to-analogue converters to settle is to provide two converters, connected in parallel, in each scaling circuit 11 of Figures 5 and 6.
  • one or the other of the converters which are supplied with the values each time the display is switched on, are connected into the scaling circuit.
  • the connection may be AND gates at the output of each converter which are opened and closed as the beams move across the screen. It is pointed out, however, that the provision of a single converter is not highly disadvantageous, since the charge-over takes place at the parabola minimum, with little or no visible effect on the image at that region. Modification of the digital values held in the store takes place as described in British Patent Specification 1,517,119.
  • the digital values for the analogue-to-digital converters 36 of Figure 7 are also held in the digital store and may be modified in the same way as the result of a test procedure as described in the prior specification.
  • the amplifiers used may be Texas Instrument amplifiers SN 4741.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • General Health & Medical Sciences (AREA)
  • Video Image Reproduction Devices For Color Tv Systems (AREA)
  • Details Of Television Scanning (AREA)

Claims (8)

1. Appareil d'affichage à tube cathodique, comportant un tube cathodique en couleur à masque perforé, des moyens aptes à balayer l'écran du tube cathodique avec des faisceaux électroniques pour afficher une information, des moyens en forme de circuit analogique (2) aptes à produire des formes d'ondes de correction de convergence pour les faisceaux électroniques lorsqu'ils balayent l'écran, une mémoire vive numérique (5) servant à mémoriser des valeurs numériques utilisées lors de la production desdites formes d'ondes de correction de convergence, des moyens (6) servant à présenter les valeurs numériques mémorisées auxdits moyens en forme de circuit (2) conformément à la position des faisceaux lorsqu'ils balayent l'écran, et des moyens (7) pour modifier les valuers numériques mémorisées afin de corriger une mire d'essai affichée sur l'écran, caractérisé en ce que lesdits moyens en forme de circuit (2) incluent des circuits (SB, 8H) de production de forme polynomiale, dont le fonctionnement de chacun est agencé de manière qu'il fournisse une forme d'onde de forme polynomiale à partir de chaque cycle d'un signal d'entrée en dents de scie, la sortie de chaque circuit de production de forme polynomiale (8B, 8H) étant raccordée à une pluralité de canaux de transmission de signaux, chacun comportant un circuit respectif (11) de réglage d'échelle qui détermine la taille de la forme d'onde polynomiale transmise dans le canal en fonction d'au moins certains desdits paramètres numériques mémorisés.
2. Appareil selon la revendication 1, dans lequel le circuit analogique (2) comporte un circuit (10) de production de X.Y, dont le fonctionnement est agencé de manière qu'il fournisse une forme d'onde représentant la fonction X.Y, X et Y étant les coordonnées des positions des faisceaux électroniques sur l'écran du tube, et dans lequel la sortie du circut (10) de production de X.Y est raccordée à plusieurs canaux de transmission de signaux, dont chacun comporte un circuit respectif (11) de réglage d'échelle, qui détermine la taille de la forme d'onde trasmise dans le canal conformément à au moins certains desdits paramètres numériques mémorisés.
3. Appareil selon l'une quelconque des revendications précédentes, comportant plusieurs circuits de sommation (9), chaque circuit étant prévu pour chaque bobine de correction (12) de tube cathodique et étant raccordé de mainère à recevoir les formes d'onde polynominale à partir des canaux, qui lui sont associés, le signal de sortie de chaque circuit de sommation étant envoyée à la bobine de correction (12), qui lui est associée.
4. Appareil selon la revendication 3, dans lequel chaque circuit de sommation (9) comporte un convertisseur numérique/analogique (36) raccordé de manière à produire un courant conformément à une valeur numérique qui lui est présentée, ce qui permet de régler la valeur du courant traversant la bobine de correction.
5. Appareil selol l'une quelconque des revendications précédentes, dans lequel le tube cathodique utilise un canon delta et dans lequel les circuits de production de forme polynomiale produisent essentiellement des formes d'ondes paraboliques.
6. Appareil selon l'une quelconque des revendications 1 à 4, dans lequel le tube cathodique utilise un canon en ligne dans lequel les circuits de production de forme polynomiale produisent essentiellement des formes d'onde du troisième degré.
7. Appareil selon l'une quelconque des revendications précédentes, dans lequel chaque moyen (11) en forme de circuit de réglage d'échelle comporte un amplificateur opérationnel (26) et un convertisseur numérique/analogique (27) raccordé par son entrée de manière à recevoir lesdites valeurs numériques et par sa sortie à une entrée (29) dudit amplificateur opérationnel.
8. Appareil selon l'une quelconque des revendications précédentes, dans lequel l'écran est subdivisé de façon imaginaire en quatre quadrants, un jeu de valeurs numériques pour chaque quadrant étant mémorisé dans ladite mémoire numérique (5), et les valeurs numériques appropriées pour chaque quadrant étant explorées par chaque faisceau électronique envoyé aux moyens en forme de circuit de réglage d'échelle (11), lorsque ce faisceau pénètre dans ce quadrant.
EP80106262A 1979-12-15 1980-10-15 Appareil de correction pour un tube à rayons cathodiques Expired EP0030595B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7943293A GB2066028A (en) 1979-12-15 1979-12-15 Digitally stored quantities for correction of crt aberrrations
GB7943293 1979-12-15

Publications (2)

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EP0030595A1 EP0030595A1 (fr) 1981-06-24
EP0030595B1 true EP0030595B1 (fr) 1984-05-16

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US (1) US4441057A (fr)
EP (1) EP0030595B1 (fr)
JP (1) JPS5947513B2 (fr)
CA (1) CA1160353A (fr)
DE (1) DE3067877D1 (fr)
GB (1) GB2066028A (fr)

Families Citing this family (10)

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Publication number Priority date Publication date Assignee Title
US4385259A (en) * 1980-12-24 1983-05-24 Sperry Corporation Dynamic convergence control apparatus for shadow mask CRT displays
US4472707A (en) * 1982-06-18 1984-09-18 Allied Corporation Display processor digital automatic gain control providing enhanced resolution and accuracy
GB2132057B (en) * 1982-09-09 1986-04-23 Link Electronics Ltd Electro-optical image correction
GB8324711D0 (en) * 1983-09-15 1983-10-19 Ferranti Plc Cathode ray tube display systems
US4757239A (en) * 1985-10-18 1988-07-12 Hilliard-Lyons Patent Management, Inc. CRT display system with automatic alignment employing personality memory
US4935674A (en) * 1988-12-27 1990-06-19 Rca Licensing Corporation Digitally controlled convergence system
JPH0748805B2 (ja) * 1990-05-28 1995-05-24 三菱電機株式会社 オート・トラッキング・モニタのｓ字補正コンデンサ切替装置
JP2813477B2 (ja) * 1991-01-31 1998-10-22 リーダー電子株式会社 表示装置を校正する方法及び装置
JPH0767122A (ja) * 1993-06-18 1995-03-10 Pioneer Electron Corp コンバーゼンス調整装置
US6636006B2 (en) * 2001-12-06 2003-10-21 Sony Corporation Deflection yoke with multiple pairs of vertical coils and switched deflection current

Family Cites Families (9)

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Publication number Priority date Publication date Assignee Title
DE3576C (de) * M. RILKE in M. Gladbach Zapfhahn mit Luftzuführung
US3308334A (en) * 1963-06-28 1967-03-07 Ibm Trace distortion correction
GB1353147A (en) * 1970-04-18 1974-05-15 Emi Ltd Scanning arrangements
US3740608A (en) * 1970-08-18 1973-06-19 Alphanumeric Inc Scanning correction methods and systems utilizing stored digital correction values
CA995810A (en) * 1971-04-29 1976-08-24 James A. Fazio Color television convergence correction
US3942067A (en) * 1974-06-21 1976-03-02 General Electric Company Multi-gun cathode ray tube convergence system
GB1517119A (en) * 1976-12-22 1978-07-12 Ibm Cathode ray tube control apparatus
US4095137A (en) * 1977-03-18 1978-06-13 Sperry Rand Corporation Digital convergence system for a multi-gun crt
GB1586201A (en) * 1977-09-15 1981-03-18 Ibm Methods of generating correction factor signals for cathode ray tubes

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JPS5694891A (en) 1981-07-31
DE3067877D1 (en) 1984-06-20
EP0030595A1 (fr) 1981-06-24
JPS5947513B2 (ja) 1984-11-19
GB2066028A (en) 1981-07-01
US4441057A (en) 1984-04-03
CA1160353A (fr) 1984-01-10

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